CVE-2025-20333

critical

Description

A vulnerability in the VPN web server of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an authenticated, remote attacker to execute arbitrary code on an affected device. This vulnerability is due to improper validation of user-supplied input in HTTP(S) requests. An attacker with valid VPN user credentials could exploit this vulnerability by sending crafted HTTP requests to an affected device. A successful exploit could allow the attacker to execute arbitrary code as root, possibly resulting in the complete compromise of the affected device.

https://www.zscaler.com/blogs/security-research/cisco-firewall-and-vpn-zero-day-attacks-cve-2025-20333-and-cve-2025-20362

https://www.theregister.com/2025/09/26/cisco_firewall_flaws/

https://www.securityweek.com/cisco-firewall-zero-days-exploited-in-china-linked-arcanedoor-attacks/

https://www.infosecurity-magazine.com/news/arcanedoor-attacks-against-cisco/

https://www.helpnetsecurity.com/2025/09/26/cisco-asa-zero-day-attacks/

https://unit42.paloaltonetworks.com/zero-day-vulnerabilities-affect-cisco-software/

https://thehackernews.com/2025/09/cisco-asa-firewall-zero-day-exploits.html

https://securityaffairs.com/182639/hacking/uk-ncsc-warns-that-attackers-exploited-cisco-firewall-zero-days-to-deploy-rayinitiator-and-line-viper-malware.html

https://www.darkreading.com/vulnerabilities-threats/cisco-actively-exploited-zero-day-bugs-firewalls-ios

https://www.bleepingcomputer.com/news/security/cisco-warns-of-asa-firewall-zero-days-exploited-in-attacks/

https://www.bleepingcomputer.com/news/security/cisa-orders-agencies-to-patch-cisco-flaws-exploited-in-zero-day-attacks/

https://therecord.media/cisco-asa-firewall-bugs-cisa-federal-agencies-warning

https://thehackernews.com/2025/09/urgent-cisco-asa-zero-day-duo-under.html

https://securityaffairs.com/182593/hacking/u-s-cisa-adds-cisco-secure-firewall-asa-and-secure-ftd-flaws-to-its-known-exploited-vulnerabilities-catalog.html

https://sec.cloudapps.cisco.com/security/center/resources/asa_ftd_continued_attacks

https://cyberscoop.com/cisa-emergency-directive-cisco-zero-days/

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-webvpn-z5xP8EUB

Details

Source: Mitre, NVD

Published: 2025-09-25

Updated: 2025-09-26

Known Exploited Vulnerability (KEV)

Risk Information

CVSS v2

Base Score: 9

Vector: CVSS2#AV:N/AC:L/Au:S/C:C/I:C/A:C

Severity: High

CVSS v3

Base Score: 9.9

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Severity: Critical

EPSS

EPSS: 0.01448

Vulnerability Watch

Tenable Research has classified this CVE under the following Vulnerability Watch classification, which includes active and historical (inactive) classifications. You can learn more about these classifications on our blog.

Vulnerability of Interest

Detections

Analytics